Learning and memory formation is a complex neurological process that consists of acquisition, storage and/or retrieval of information. Hippocampus is one of essential components of brain that is responsible for long term memory formation which requires de novo RNA and protein synthesis, and declines with increase of age. Although progresses have been made in defining the anatomic areas and elucidating the importance of synaptic plasticity in learning and memory in the past three decades, the molecular mechanisms underlying learning and memory formation as well as the aging influences in this process is largely unknown. In an attempt to dissect the memory process at the molecular level, we used cDNA microarray to analyze the changes of rat hippocampal gene expression before and after maze training (T-stone and water maze) and between young- and old-rats. After analyzing over mouse 16,000 unique cDNA clones, we found several genes that were up- regulated in maze trained hippocampus in both young and old rats and identified differentially expressed genes between young and old rats. Currently, we are characterizing the structure and functio - Learning and memory, rat, hippocampus, gene, aging